1. Field of the Invention
The present invention relates generally to a disk cassette which rotatably houses a disk-form information recording medium in a cassette casing defining an opening or aperture to allow access of the recording medium by an information recording and/reproducing device in a disk drive apparatus, and which has a sliding shutter operably closing the aforementioned recording medium access aperture. More specifically, the invention relates to an improvement for a sliding shutter arrangement which is suitable for readily fitting onto the cassette casing of a disk cassette, such as a magnetic disk cassette, and for facilitating dust-proofing cover for the recording medium access aperture.
2. Description of the Background Art
Disk cassettes such as those used to house rotatable magnetic disks in a cassette casing, are provided with one or more disk access openings through the cassette casing. However, due to the sensitive nature of the disk surfaces it is desireable to automatically cover the access opening when the disk is not in use. An example of a disk cassette which provided with such means can be found in U.S. Pat. No. 4,445,155. This document is assigned to the common assignee to the present invention. This type of arrangement is widely marketed in the form of a 3.5 inch disk cassette for use in computers and the like type of devices. The disk housed in this type of the cassette casing has at least one surface which is conditioned to record data and which is adapted to be driven by known types of disk drive apparatus. The cassette casing is provided with at least one disk access aperture or opening through which a magnetic recording and/or reproducing head can be inserted in a manner to closely juxtapose the recording surface of the disk. A sliding shutter is mounted on the cassette casing for selectively opening and closing the access aperture. This shutter is adapted to close the opening when the disk is not in use and to be slidable to a position in which an offset opening formed therein coincides the access aperture when the disk is inserted into a disk drive.
This arrangement has basically proven satisfactory however, hithertofore proposed shutters have been formed so as to have an essentially U-shaped cross-section wherein a long narrow edge which defines the bottom of the U-shape and two flat plate-like portions which depend from the narrow edge define the legs of the U-shape.
In order to operatively connect this arrangement to the case of the cassette, a groove has been formed in the external surface of one of the halves of the cassette and one leg of the shutter formed with a pair of projections which are slidably received in the groove. When assembled, the other leg of the shutter slides on the flat face of the other side of the other half or shell of the casing. When assembling this arrangement it is necessary to spread the legs of the U-shaped arrangement when fitting the same onto the case. This tends to bend the member some instances resulting in excessive play, improper sliding characteristics or the like.
In addition to this the guide groove is relatively shallow, the projections received therein accordingly narrow and the U-shaped legs of the shutter relatively flexible, whereby it is relatively easy for the shutter to be spread open to the degree that it can accidentally detach from the case.